package com.ihr360.job.core.step.skip;

import org.springframework.classify.BinaryExceptionClassifier;
import org.springframework.classify.Classifier;

import java.io.FileNotFoundException;
import java.util.Collections;
import java.util.Map;

/**
 * <p>
 * {@link SkipPolicy} that determines whether or not reading should continue
 * based upon how many items have been skipped. This is extremely useful
 * behavior, as it allows you to skip records, but will throw a
 * {@link SkipLimitExceededException} if a set limit has been exceeded. For
 * example, it is generally advisable to skip {@link FlatFileParseException}s,
 * however, if the vast majority of records are causing exceptions, the file is
 * likely bad.
 * </p>
 *
 * <p>
 * Furthermore, it is also likely that you only want to skip certain exceptions.
 * {@link FlatFileParseException} is a good example of an exception you will
 * likely want to skip, but a {@link FileNotFoundException} should cause
 * immediate termination of the {@link Step}. A {@link Classifier} is used to
 * determine whether a particular exception is skippable or not.
 * </p>
 *
 * @author Ben Hale
 * @author Lucas Ward
 * @author Robert Kasanicky
 * @author Dave Syer
 * @author Dan Garrette
 */
public class LimitCheckingItemSkipPolicy implements SkipPolicy {

    private int skipLimit;

    private Classifier<Throwable, Boolean> skippableExceptionClassifier;

    /**
     * Convenience constructor that assumes all exception types are fatal.
     */
    public LimitCheckingItemSkipPolicy() {
        this(0, Collections.<Class<? extends Throwable>, Boolean> emptyMap());
    }

    /**
     * @param skipLimit the number of skippable exceptions that are allowed to
     * be skipped
     * @param skippableExceptions exception classes that can be skipped
     * (non-critical)
     */
    public LimitCheckingItemSkipPolicy(int skipLimit, Map<Class<? extends Throwable>, Boolean> skippableExceptions) {
        this(skipLimit, new BinaryExceptionClassifier(skippableExceptions));
    }

    /**
     * @param skipLimit the number of skippable exceptions that are allowed to
     * be skipped
     * @param skippableExceptionClassifier exception classifier for those that
     * can be skipped (non-critical)
     */
    public LimitCheckingItemSkipPolicy(int skipLimit, Classifier<Throwable, Boolean> skippableExceptionClassifier) {
        this.skipLimit = skipLimit;
        this.skippableExceptionClassifier = skippableExceptionClassifier;
    }

    /**
     * The absolute number of skips (of skippable exceptions) that can be
     * tolerated before a failure.
     *
     * @param skipLimit the skip limit to set
     */
    public void setSkipLimit(int skipLimit) {
        this.skipLimit = skipLimit;
    }

    /**
     * The classifier that will be used to decide on skippability. If an
     * exception classifies as "true" then it is skippable, and otherwise not.
     *
     * @param skippableExceptionClassifier the skippableExceptionClassifier to
     * set
     */
    public void setSkippableExceptionClassifier(Classifier<Throwable, Boolean> skippableExceptionClassifier) {
        this.skippableExceptionClassifier = skippableExceptionClassifier;
    }

    /**
     * Set up the classifier through a convenient map from throwable class to
     * boolean (true if skippable).
     *
     * @param skippableExceptions the skippable exceptions to set
     */
    public void setSkippableExceptionMap(Map<Class<? extends Throwable>, Boolean> skippableExceptions) {
        this.skippableExceptionClassifier = new BinaryExceptionClassifier(skippableExceptions);
    }

    /**
     * Given the provided exception and skip count, determine whether or not
     * processing should continue for the given exception. If the exception is
     * not classified as skippable in the classifier, false will be returned. If
     * the exception is classified as skippable and {@link StepExecution}
     * skipCount is greater than the skipLimit, then a
     * {@link SkipLimitExceededException} will be thrown.
     */
    @Override
    public boolean shouldSkip(Throwable t, int skipCount) {
        if (skippableExceptionClassifier.classify(t)) {
            if (skipCount < skipLimit) {
                return true;
            }
            else {
                throw new SkipLimitExceededException(skipLimit, t);
            }
        }
        else {
            return false;
        }
    }

}